Welded brake shoe assembly



Feb. 25, 1958 s. K. WELLMAN 2,824,629

WELDED BRAKE SHOE ASSEMBLY Filed Dec. 17, 1955 3 Sheets-Sheet l r N I56$ INVENTOR. SAMUEL K. WELLMAN I5 BY fiJMMfl/MW ATTORNEY.

Feb. 25,1958 5. K. WELLMAN 2,824,629

WELDED BRAKE SHOE ASSEMBLY Filed Dec. 17, 1953 5 Sheets-Sheet 2 FIG. 2

. O INVENTOR.

SAMUEL K.WELLMAN ATTORNEY Feb 25, 1958 s. K. WELLMAN 2,824,629

WELDED BRAKE SHOE ASSEMBLY Filed Dec. 17, 1953 s Shee ts-Sheet a FIGSINVENTOR. SAMUEL K. WELLMAN ATTORNEYS United States Patent WELDED BRAKESHOE ASSEMBLY Samuel K. Wellman, Cleveland Heights, Ohio, assignor to S.K. Wellman Company, Bedford, Ohio, a corporation of Ohio ApplicationDecember 17,1953, Serial No. 398,686. Claims. (Cl. 188-234) Thisapplication is a continuation in part of my copending application S. N.112,476, filed August 26, 1949.

This invention relates to brakes for use in checking and stepping thespeeds of rotating members and particularly relates to arcuate vehiclebrake shoe members and arcuate sintered powdered metallic linings orfriction facings and to apparatus and methods for assembling suchlinings upon such shoe members.

The most common vehicle brake is of the type comprising a brake drumhaving a cylindrical braking flange and two internal-expanding arcuatebrake shoes carrying friction linings adapted to be contacted with thebraking flange of the drum by expansion or outward movement of eachbrake shoe. The shoes are generally formed of solid metal such as steelor aluminum alloys and provided with friction linings of non-metallicmaterials such as asbestos with a rubber or other plastic binder. Thelining is secured to each shoe by rivets extending through both the shoeand lining or by adhesive bonding. Adhesive has the disadvantage ofrequiring long processing time (e. g., for baking) and adhesive has thefurther disadvantage of interfering with heat transfer and the use ofrivets is disadvantageous because of poor heat transfer and because,when the lining becomes worn, the rivets become exposed and score theinner surface of the brake drum and also because a riveted lining islikely to break at any time across rivet openings and injure or ruin thelining, and the cooperating brake drum.

Further, the non-metallic friction linings are subject to numerousdisadvantages, for example, they have their characteristics greatlychanged by contact with oil, grease, or water, have theircharacteristics greatly changed by temperature and are unable to conductaway the heat generated during operation. In some cases heating of thefabric lining is sufficient to melt or fuse the bonding components andcompletely destroy the anti-friction properties of the lining.

Friction articles of powdered predominantly metallic material, sinteredand bonded to a metallic backing memher, are well known to the art andhave numerous advantages over fiber facings, the sintered facings beingless susceptible to changes in temperature and atmospheric conditions,less affected by oil, grease and foreign matter, much more conductive'of heat, and showing less wear with the same use.

Friction articles of the type referred to are produced by pressing 'orbriquetting powders of suitable composition usually comprising metalspredominantly and containing .minoramounts of non-metallic ingredientssuch as graphite. The briquette or compact so formed is later heated toa .sintering temperature, but because the metal powder even whensintered is rather porous and of low tensile strength, it is customaryto provide a reinforcing backing plate as of steel and generally the'sintermg ,step is accomplished with the briquette held against a cleanand properly prepared surface of the backing plate. The heat of thesintering step causes the pressed powder to sinter together and tointegrally bond to the backing .plate.

While the properties including good heat conductivity of sinteredmetallic linings, unaffected as they are by contact with liquids or byvariations in temperatures, pressures or speeds, would appear toadmirably adapt them to vehicle brake uses, it has not been foundfeasible heretofore to do so due to the difficulty of properly designinga brake member, the difficulty of working or machining the sinteredmetal compositions, and particularly due to the difficulty of providinga removable bond between a brake shoe and a sintered metallic lining.

Due to lack of tensile strength, the sintered materials are so brittlethat attempts made to rivet them to a brake shoe by rivets extendingthrough or beneath the material have not been successful, for thematerial is either broken during the drilling of holes for rivets, orduring the riveting operation, or it quickly breaks in service, thebreaks usually occurring at the rivet holes. Further, this same lack oftensile strength prevents the metallic friction materials from beingreadily bent to shape so that, unlike asbestos, they cannot be merelybent around an arcuate surface and simply secured thereto by heretoforeknown methods.

While, attempts to preform or roll bend the sintered facing and itsbonded backing, before attaching them to the shoe, have been previouslyknown, e. g., as described and claimed in U. S. Patent 2,446,891,entitled Method of Shaping Birnetallic Articles and issued August 10,1948, upon an application filed by Charles H. Tower and Francis J.Lowey, still there arises the problem of attachment, rivets not beingsatisfactory for reasons previously explained, adhesive bonding notbeing saisfactory from the standpoint of strength and of difiiculty ofremoval and of so seriously interfering with heat conductivity as tonegative one of the most important advantages of the predominantlymetallic facing material, and welding (either by tack welds at the sidesof facing and shoe or throughout the contiguous lengths of facing, orits immediate backing, and the shoe member) presenting difficulties inmany applications from the standpoint of processing time and expense andinsuperable maintenance difficulties because an old lining or itsbacking, if so welded, cannot be ripped off of the shoe when a new oneis to be put on in its place.

It is an object of the present invention to provide simple andinexpensive means for overcoming the above mentioned difiiculties.

A further object of the invention is to provide a new and improvedinternal-expanding brake shoe and lining assembly for use in vehiclebrakes and characterized by an integral imperforate friction surface.

Another object of the invention to provide a novel brake shoe having asintered predominantly metallic .friction surface and characterized bygreat strength, relative- 1y low weight, smooth friction surface, andeasy removal for maintenance purposes.

Other objects and advantages will become apparent and the invention maybe better understood from consideration of the following descriptiontaken in connection with theaccompanying drawing, in which:

Fi l is a perspective view of a portion of a brake shoe and sinteredpowdered predominantly metallic brake lining assembly being attachedthereto in accordance with the invention;

Fig. 2 is a diagrammatic side view (partly in section) of a weldingapparatus showing a method of attaching the sintered brake lining andbrake shoe in accordance with the invention;

Fig. 3 is a front view of the welding apparatus of Fig. '2; and,

Fig. 4 is a diagram of an electric and pneumatic circuit found useful inconnection with the apparatus and according to one aspect of the methodof the invention.

Referring now to Figs. 1 and 2, there is shown a brake shoe member 10which comprises a web plate 11 curved edgewise and a thick flangeportion or sole plate 12 curved flatwise and conforming to the curvatureof a brake drum (notshown). The brake shoe member 10 which thus is ofT-shape in cross section, constitutes one of the usually two expandingbrake shoes for one of the brake drums of a motor vehicle. The web plate11 is provided with one or more openings 13 for attachment of .brakeshoe actuating mechanism as is usual in suchconstruction. The flange 12at each side of the web 11 is provided with openings 14 for receivingnovel brake lining fastening means as will be described. The openings 14may be the usual holes for usual rivets, allowing the use of a standardbrake shoe in practicing the invention even though a riveted lining isnot to be used.

In accordance with the stated objects, a sintered predominantly metallicmixture of friction materials 15 is to be secured to the above describedbrake shoe member 10.

It has been found essential that sintered compositions useful asfriction surfaces on brake lining members be produced in flat form ifthey are to have uniform properties. Articles of large area such as arerequired for brake linings must be pressed and pressed flat if they areto have uniform density, hardness and friction properties. In accordancewith prior practices, such flat pressed shapes may then be assembled ona clean and properly prepared surface of a flat steel backing member andthe assembly then pressed and heated to a sufiicient temperature and fora sufficient length of time to sinter the pressed mixture and cause itto integrally bond to the steel backing. To achieve the proper bond itis necessary that the pressed mixture and the steel backing be heldtogether while flat and under pressure. The

unitary article (of friction facing bonded to a steel backing) thusproduced is now a flat straight member and is in condition to be made toconform to the brake shoe to which it is later attached. Of course, itis much too stiff (and breakable) to be wrapped around by hand like anasbestos lining. Due to the abrasive character of the friction producingmaterials in the friction facing mixture, it is practically impossibleto machine or grind the resultant article to curved shape, and becauseof the low tensile strength of the sintered metal brake lining 15 it isnot possible to bend this lining by resorting to the usual bending pressfor in such bending the sintered surface would chip and crack badlybecause of its low tensile strength. But, by passing the flat brakelining with its steel backing member (16) between pressure rolls, seefor example the apparatus described in the above mentioned patent, thesintered brake lining 15 and its steel backing member 16 may be causedto conform to the curvature of the convex brake shoe 10 by applyingpressure to laterally extending areas of bonded facmg and backingsuccessively and progressively along their lengths.

In accordance with the present invention, the steel backing member 16and consequently the friction facing 15, is held in place on the brakeshoe and then secured to the brake shoe 10 by welds performed in theholes '14 In the illustrated embodiment the welds are made by usmg pins17 one in each of these holes. Preferably, the pms are slightly smallerthan the holes so that the pins will not weld to the sides of the holes14 to any great extent.

The pins 17 are attached or applied one at a time beginning at thecenter of the brake shoe on one side of the web and Working from thecenter toward the ends and then repeat on the other side of the web.When the lining requires replacing, the lining and backing members aretorn from the brake shoe and the pins forced 4 out of the openings inthe brake shoe flange and new lining is then attached as originallyapplied.

I do not mean to limit the present invention to a case where the pinsare preheaded (like the pin 17 to the right of flange 11 in Fig. 1) forI have found that good results can be obtained when using straight sidedpins and then depending upon upsetting to form heads during the Weldingoperation. On the other hand, ordinary rivets (i. e., headed pins) maybe used but they are used not at all like rivets in ordinary practice,for while a rivet head may be used to secure a headed pin 17 to the faceof flange 12, Without the necessity of making a weld or upset at thispoint, the inner-most end of such a rivet obviously cannot be peenedover as in ordinary riveting, and, instead, it is pin welded to theadjacent backing, at the side of the latter opposite the frictionfacing.

Alternatively, pins need not be used at all for I have found it feasibleto merely use an ordinary welding rod, strike an arc in each rivet holeand fill the hole with molten material. However, the pin welding methodis preferred, because during production it assures consistently goodwelds, together with feasibility of later removal of weld fasteninglining. Of course, it is apparent that this is a matter controlled bythe size of the pins,

the amount of current used in the welding operation and the surfacecondition of the holes in the brake shoe. A slight welding to the brakeshoe is not objectionable and may even be beneficial. However, thewelding time and current should not be so severe as to render the entirepin body molten, so that it will weld against the sides of the opening14 and prevent ready removal of pins and lining. T secure a welded jointbetween pin and shoe might result in bending and destruction of the shoein removing the pin and thus prevent its re-use.

As seen in Fig. 2 the superposed brake shoe and lining and backingassembly -16, with one or more pins 17 inserted, is placed in a weldingapparatus comprising a base support 19 which carries a laminated core 20surrounding a primary winding 21 and a secondary winding 22. Primaryvoltage may be 220 volts, A. C., and although it depends on the size ofthe pins, for steel rivets, 0.155" in shank diameter, the secondary orwelding voltage of the welder may be as follows:

Secondary voltage volts 3.1 Time of weld second 0.l0

The secondary coil 22-23 is composed of a single part turn or coilformed as a horizontally arranged U with one arm (23) vertically abovethe other. The U is resilient and normally holds the upper arm 23 in itsuppermost position when a piston is released as will presently appear.The lower arm 22 is stationary and passes through an opening in the core20 beneath the primary coil and seats on a metallic block 24 which maybe made of steel and is provided with internal threads 25 for receivinga lower welding electrode adjusting stud 26. Block 24 is seated upon aninsulated block 27 which is secured to the base 19 by bolts 28 (see Fig.3). As is also shown in Fig. 3, the secondary lower stationary arm 22,the block 24 and the insulating block 27 may be held together by bolts29.

A'lower fixed welding electrode indicated generally at 30 comprises adeformable rubber cushion 31 covered by a resilient strap 32 of aconductive metal such as copper, with deformable cushion and resilientstrap being contained in and upon a metal cup 33 which is mounted uponor formed integral with the adjusting stud 26. A jam nut 34 is used forlocking this fixed electrode at any predetermined position.

' An upper movable terminal indicated generally at 40 is attached to theupper secondary arm 23 and comprises an electrode 41 of conductive metalheld (as by a Morse taper) in a metallic holder 42 which in turn issupported by an adjusting stud .43 which is externally threaded andprovided with a lock nut 44 foradjustably securing the terminal assemblyto the stud. Additional lock nuts 45, 46 adjustably secure the secondaryupper arm 23 upon the stud.

Because it is desired to clamp the brake shoe flange 12', and the lining16 and its backing 15, securely without subjecting these members to anycurrent except that passing through an individual pin 17, .the upperelectrode assembly also has a bifurcated metallic clamp 35 biaseddownward by helical springs 36 away from a metallic support member 47which is insulated from the electrically operative part of the assemblyby insulating washers 48 and 49. Stripper bolts 50 serve to laterallylocate the springs 36 and have their main shanks forming a clearancewith holes provided therefor in clamp 35 and reduced diameter threadssecuring these bolts to support member 47.

The externally threaded upper terminal adjusting stud 43 is bored outand internally threaded at its upper end 51 to accommodate a threadedend 52 of a piston rod attached to a piston 53 contained in a fluidpressure cylinder 54 and in which the piston may be normally biasedupward by a helical spring 55. A fluid pressure conducting conduit 56leads to the top of the cylinder housing 54. As shown in the drawing thecylinder housing is supported by a bracket 57 which is secured to themain assembly as by bolts 58 which also serve to hold the laminationstogether at their tops. At their bottoms the laminations are heldtogether by bolts 59 which engage support angles 60 which in turn arefastened by other bolts 61 (Fig. 2) to the base 19.

From the above it will be apparent that suitable means are provided forclamping the work to be welded between the terminals of the welder.Suitable means are also provided for applying welding current almost im-.mediately thereafter as may be understood from reference to 'Fig. 4 inwhich is diagrammatically shown conduit 56 tapped into a house line 68of fluid pressure (such as a 90 p. s. 'i. compressed air line) with afoot valve 69 interposed between the source and the cylinder. Interposedbetween foot valve 69 and the cylinder 54 is a pressure responsiveelectric circuit making switch 70. Preferably, the pressure responsevalue of the pressure responsive switch is such that piston 53 will havepractically completed its movement responsive to pressure introduced asthe foot valve 69 is operated before the pressure will have built upsufficiently for switch 70 to close the associated circuits.

The equipment is powered from a main line 60 (e. g., of 60 cycle, 220volts) and when pressure switch 70 closes its contacts 62-63 conductscurrent through normally closed contact 64 of a timer 65 to energize asolenoid coil 66 to close a main contact 67 and energize the primarywinding 21 and, consequently, the secondary circuit. After apredetermined time interval (such as the .025 second previouslymentioned) timer 65 which has been energized through theauxiliary-contact 62 (on .pressure switch 70) operates to open thecircuit to solenoid coil 66 and deenergize primary winding .21 andsecondary windings 2223.

When it is desired to attach a brake lining assembly 15, 16 to a brakeshoe flange 12 the assembly is pushed against the brake shoe with theconvex side of the flange facing downward and with one of the flangeopenings 14 directly above the lower electrode as shown in Figs. 2 and3. The brake shoe and lining are clasped together in vertical relation,first by the hand of the operator and later, as the foot switch isoperated, by the upper resiliently mounted clamp 35 and by the lowerresilient electrode assembly 30, with both the upper and lower clampingmembers conforming to the arcuate shape of the work. Of course, beforethe mechanical clamping takes place, a welding pin or stud or headedrivet 17 will have been pushed into a hole 14 with its lowermost endagainst the upper surface of the backing member 16 and with its upperand directly beneath the upper electrode 41. As compressed air isadmitted-to the cylinder 54, the pin 17 is clamped against the steelbacking member 13, and then the welding circuit fires and during theinstant between the time that the main contact 67 is closed and thenormally closed timer 64-65 is opened, the current from the line 60energizes primary winding 21, energizing the secondary 22-23 and causinga welding current to pass through the electrode for a fraction of asecond thus welding the adjacent end of the pin 17 to the steel backingmember 16.

Sintered predominantly metallic brake linings with their steel backingmembers bent to conform to the flange of a brake shoe are now adapted tobe supplied to the trade as separate articles of manufacture and may beeasily and readily attached to the flanges of brake shoes by anyordinary mechanic with the aid of a pin welding machine of the typedescribed. The attaching of the brake lining to the brake shoe merelyinvolves properly positioning the brake shoe on the brake lining betweenthe two'electrodes with the concave side uppermost then putting a pinthrough a hole in the brake flange, resting it against the backingmember, applying pressure to the pin and simultaneously or sequentiallyclosing an electric circuit through the pins separately one at a timefor welding the remote end of each pin to the backing member and (ifstraight sided pins are used) for upsetting the inner end of the pin.

Since the electrical demand of the welding apparatus described iscomparatively small, it is inexpensive to install and may be operated onthe conventional current usually found in almost any shop associatedwith gasoline filling stations and the like. With it, practically anyworkman can easily and quickly change or install new metallic brakelinings on brake shoes for most types of automobile brakes. Since thesintered brake lining is not perforated or its surface broken inattaching the same to the brake shoe, the brake lining is very enduringand lasting as well as being very eflicient in checking and stopping thespeed of automobiles and like vehicles on which it is installed.

With the brake shoe mechanism disclosed in the pres ent application, andalso with brake shoe mechanism described and claimed in my abovementioned copending application, of which this is a continuation inpart, the brake lining comprises a backing member to which is bonded byheat and pressure a layer of sintered powdered material predominantlymetallic and the backing member is in turn attached to a brake shoemember by rigid metallic means requiring the use of welding apparatus.The arrangement of the invention of the present application uses twobacking members, one immediately back of the sintered material and theother (an integral or component part of the shoe member) being providedwith holes through which welded means extend to be welded to the firstmentioned backing at its side opposite the side to which the sinteredmaterial is bonded. This makes possible the ready removal andreplacement of worn brake lining without the disadvantages of rivetsextending through the lining or its immediate back. Thus, there need beno interruption of the continuity of the friction surface of the brakelining and as a result the lining does not normally wear out so fast orbreak so soon, because the sintered friction surface is smooth andunbroken, that is, it is not penetrated by pins, rivets, or otherfastening means that are conducive to chipping or fracturing of thesintered surface of the lining, or to scoring of the brake drum.Further, the arrangement of the invention prevents distinct advantagesboth from the standpoint of heat transfer during operation and laterwhen the time comes for lining replacement because the pin weldedbacking is easy to strip off (with a chisel or large pliers), whereasordinary welds suitable for an application of the type described arevery stubborn and just about impossible 7 to break 'or remove when itcomes time to remove them in order to present clean surfaces forreplacement purposes, and ordinary adhesives are also stubborn andrequire long periods of soaking and scraping in order to remove them.

The arrangements of the invention make it possible to weld togetherplates of any thickness because it is not necessary to use a pressuresuflicient to deform the plates in order to pinch them together at theweld points. The process and apparatus of the invention makes itpossibleto Weld Without protecting the eyes (because the weld is notexposed), makes it possible to weld with very low current values, and,insofar as brake linings are concerned, makes it possible to havequieter brakes (because of more secure fastening), makes it possible tohave longer wearing brakes (because of better heat conduction and norivets or perforations in the lining), and eliminates the need fordrilling or otherwise providing holes or indentations in a brake lining.

The invention has been described with particular reference to vehiclebrakes having outwardly expanding shoes but it is apparent that theinvention is not so limited and applicable to other applications, forwhile I have illustrated and described a particular embodiment, vari ousmodifications may be made without departing from the true spirit andscope of the invention as defined in the accompanying claims which areintended to include all reasonable equivalents.

I claim as my invention:

1. As an article of manufacture, a metallic brake shoe assemblycomprising an imperforate predominantly metalic sintered brake lininghaving a metallic backing plate integrally bonded thereto substantiallyco-extensive therewith, a web plate curved edgewise and disposed in asingle plane, a flange portion disposed in part-cylindrical curvatureand formed integral with the convex edge of the web plate, with saidmetallic hacking plate being curved similarly to said flange portion andwith the flange perforated and pins extending through the flange portionperforations welded to the backing plate for removably securing thebacking plate to the flange portion.

2. In a braking device, a brake shoe member T-shape in cross sectioncomprising a flat arcuate metallic web plate forming the stern of the T,and forming the head of the T a rigid flange portion, a relativelyflexible metallic backing, and a sintered body of metallic andnonmetallic powders, with the flange portion conforming to the curvatureof the web plate and rigidly secured thereto and extending to eitherside thereof and having perforations at either side of the flange plate,the backing member curved flatwise to conform to the curvature of theflange portion and welded thereto at the perforations by pin weldingmeans comprising headed rivets having their shanks extending through theperforations, and the sintered body being bonded to the backing memberto form an imperforate brake lining layer.

3. A braking device as in claim 2, further characterized "by theimperforate outer brake lining layer being con- 8 tinuous and uniform inthickness and bonded to the backing member substantially continuouslythroughout the entire engaged surfaces of both.

4. A brake shoe and lining assembly of the type having a friction facingcomprising a mixture of sintered metallic and non-metallic powdersintegrally bonded to a metallic backing member and having a brake shoesupport member comprising a web extending at right angles to said facingand backing member, in which said friction facing is imperforate,continuous and uniform in thickness, in which the support membercomprises a Web portion curved edgewise and a perforated flange disposedin'part-cylindrical curvature and integral with the convex edge of theweb portion, in which the backing member is curved similarly to theflange portion, and in which pins are welded in the flange portionperforations so as integrally to bond the backing member to the supportmember.

5. As an article of manufacture, a composite metallic brake shoe forautomotive brakes of the type having a cylindrical brake drum adapted toenclose a plurality of internal expanding brake shoes of T-shapedtransverse cross section; said shoe consisting of a relatively flat,rigid, arcuate web plate forming the stem of the T and having at leastone opening therethrough for the attachment of brake operating means, arelatively thick, rigid self supporting sole plate arcuately curvedaround the outer edge of said web plate and forming the head of the Twith the inner concave surface of said sole plate directly andpermanently attached to said web plate and said sole plate havingopenings extending therethrough on either side of the web plate; incombination with an external convex friction facing assembly comprisinga relatively flexible imperforate backing plate of solid metal andbonded thereto under heat and pressure an imperforate porouspredominantly metallic sintered layer of homogeneous compositionthroughout extending continuously and uninterruptedly across the convexexternal face of said sole plate; together with welding means extendingthrough said openings in said sole plate and extending to a weldedengagement with said relatively flexible backing plate at the facethereof opposite the face to which said predominantly metallic sinteredlayer of 5 homogeneous composition is bonded.

References Cited in the file of this patent UNITED STATES PATENTS1,174,446 Rietzel Mar. 7, 1916 1,756,936 Bendix May 6, 1930 1,762,694Long et al June 10, 1930 1,864,929 Peterson June 28, 1932 1,907,483Blume May 9, 1933 1,909,256 Emmord May 16, 1933 1,946,061 Budd Feb. 6,1934 2,057,753 Whitworth Oct. 20, 1936 2,067,363 Waeschle Jan. 12, 19372,277,107 Imes Mar. 24, 1942 2,381,941 Wellman et al Aug. 14, 1945

